#include "../include/pit.h"

//https://wiki.osdev.org/Programmable_Interval_Timer

/*
Bit/s        Usage
7            Output pin state
6            Null count flags
5 and 4      Access mode :
                0 0 = Latch count value command
                0 1 = Access mode: lobyte only
                1 0 = Access mode: hibyte only
                1 1 = Access mode: lobyte/hibyte
3 to 1       Operating mode :
                0 0 0 = Mode 0 (interrupt on terminal count)
                0 0 1 = Mode 1 (hardware re-triggerable one-shot)
                0 1 0 = Mode 2 (rate generator)
                0 1 1 = Mode 3 (square wave generator)
                1 0 0 = Mode 4 (software triggered strobe)
                1 0 1 = Mode 5 (hardware triggered strobe)
                1 1 0 = Mode 2 (rate generator, same as 010b)
                1 1 1 = Mode 3 (square wave generator, same as 011b)
0            BCD/Binary mode: 0 = 16-bit binary, 1 = four-digit BCD
*/

#define PIT_COMMAND_PORT 0x43
#define PIT_DATA_PORT 0x40

void pit_init(int freq) {
    int divisor = 1193180 / freq;
    uint8_t command = 0x36;//00110110 see above to get the idea wtf is this number

    outb(PIT_COMMAND_PORT, command);

    outb(PIT_DATA_PORT, divisor & 0xFF);
    outb(PIT_DATA_PORT, divisor >> 8);
}